Called BRIGHTs, the tiny probes described in the online issue of Advanced Materials on Nov. 15, bind to biomarkers of disease and, when swept by an infrared laser, light up to reveal their location. Tiny as they are, the probes are exquisitely engineered objects: gold nanoparticles covered with molecules called Raman reporters, in turn covered by a thin shell of gold that spontaneously forms a dodecahedron.